Triangular glass knives used for cutting in ultramicrotomy are typically produced by the user. This ensures that a high-quality triangular glass knife having a specific dimension and a specific cutting angle with respect to the specimen section is met according to its desired requirements.
The glass knives are produced from commercially available glass strips, for example, having a length of 400 mm. These glass strips are first repeatedly broken symmetrically until individual glass squares are obtained. The glass squares each are broken along the respective square diagonal so that two individual triangular glass knives with a cutting angle, for example, of 45.degree. are formed.
It has been found that the glass squares do not break exactly along their angle bisector (e.g., 45.degree.). Scoring and breaking the glass square along the angle bisector always leads to an uncontrolled breakage, forming an unusable or unacceptable triangular glass knife. For this reason, the glass square is not scored exactly along its angle bisector but slightly offset from it. In this arrangement, the score line intersects the diagonal in the center point of the square. This provides two individual triangular glass knives, each with a sharp edge suitable for cutting and a blunt break point.
An appliance that fulfills the production requirements of triangular glass knives of this kind is known from the LEICA publication Reichert Knifemaker, Knifemaker zum symmetrischen Glasbruch (translated Reichert Knifemaker, Knifemaker for Symmetrical Breakage of Glass), 2.K.-Reichert EM-Laboratory-D-3/93, 1993. This appliance has a scoring wheel arranged in a fixed location and a device provided in a fixed location for applying a breaking force. To hold the glass squares, the Reichert Knifemaker is equipped with two individual clamping jaws having a U-shaped profile, which are designed to be displaceable, independently of one another, laterally and parallel to one another. Adjustments are necessary to align the glass square beneath the scoring wheel and to set the required score line.
Due to the independent adjustability of the two clamping jaws and the required setting precision, making adjustments is relatively time-consuming. Adjustments have to be made every time, for example, when a different score angle is needed or the scoring wheel is changed. Readjustments are also necessary for glass strips that originate from different manufacturers.
Accordingly, there is a need for a device for forming triangular glass knives of the type described in the Reichert Knifemaker that provides simplified handling and yet precisely orients the glass squares. The present invention meets this need.